A component may become damaged over time due to erosion or impact by foreign object to the component. As a result, the damaged component may be repaired by adding material to the damaged component. In one example, the component may be a compressor blade, compressor vane, turbine blade, or turbine vane which has been damaged due to impact with a foreign object. Such blades or vanes may be repaired by adding layers of material to the damaged portion to rebuild the damage component. One method of repairing such damaged components is laser deposition or additive manufacturing.
Laser deposition is typically performed in layers at a fixed working distance between a laser head and a metal substrate of a workpiece. The laser head produces a melt pool in the metal substrate of a surface of the workpiece. Metal powder is then injected at a powder flow rate into the melt pool via a nozzle. The melt pool is cooled to produce a build layer having a specific microstructure.
As the thermal boundary conditions of the workpiece change, for example when the substrate geometry changes, it may become necessary to increase the powder flow rate to maintain the same cooling rate of the melt pools to produce the desired microstructure of the build layer. As an example, corners and edges of the workpiece may have less ability to act as a heat sink and, as such, may require an increased powder flow rate to prevent melt-back and improve draft angles.
However, fixed working distances are not able to maintain constant cooling rates in the laser deposition if the substrate geometry is changing. Increasing and/or decreasing powder flow rate would allow dynamic adjustment of the cooling rate of the melt pools. However, typically, the powder flow rate is adjusted at a powder feeder and the system response, as observed at the melt pool, is delayed by several seconds while the flow stabilizes. As such, powder flow rate has been typically a set and forget arrangement because it is not adequately adjustable within the timescales needed.